LXXII. Nuclear interactions of great energy.—Part I. Evidence for the creation of heavy mesons

Summary The masses of charged mesons, produced among the ‘shower’ particles in the nuclear interactions of protons of great energy have been determined by scattering and grain-density measurements. For energies greater than 50 Bev heavy mesons of mean mass ∼1300 me , provisionally identified as κ-mesons, are produced with a frequency comparable with that of the π-mesons. Evidence for the creation of such heavy mesons is also provided by an observed decrease in the ratio of neutral π-mesons to shower particles at very high energies. A method is described for measuring the lifetime of the neutral φ-meson, which takes advantage of the existence of an alternative mode of decay : φ0→γ+β++β− . It is shown that the proportion of φ-mesons which decay in this second mode is not greater than 4%. The preliminary observations suggest that the mean lifetime is about 10−14 see.